Control system for a two-stroke locomotive diesel engine having an exhaust aftertreatment system

ABSTRACT

The present application generally relates to a diesel engine and, more particularly, to a control system and method for an exhaust aftertreatment system for a locomotive diesel engine. In accordance with an embodiment of the present system, a two-stroke uniflow scavenged diesel engine system including an exhaust aftertreatment system is described for reducing NO x  emissions and achieving desired fuel economy. More specifically, a system and method for controlling the exhaust aftertreatment system is provided. The present system being adapted to monitor and control select components of the exhaust aftertreatment system. Specifically, the control system may be adapted to control select components of an exhaust aftertreatment system to adaptively regulate filtration based on various operating conditions of the locomotive.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Nonprovisional Patent Application, which claimsbenefit to U.S. Provisional Application Ser. No. 61/388,443, entitled“Exhaust Aftertreatment System for a Locomotive,” filed Sep. 30, 2010,the complete disclosure thereof being incorporated herein by reference.

TECHNICAL FIELD

This application relates to a locomotive diesel engine and, moreparticularly, to a system and method for controlling or an exhaustaftertreatment system for a locomotive diesel engine.

BACKGROUND OF THE DISCLOSURE

The present application generally relates to a locomotive diesel engineand, more specifically, to a system and method for controlling anexhaust aftertreatment system for a locomotive diesel engine. Thepresent exhaust aftertreatment systems may be implemented with alocomotive two-stroke uniflow scavenged diesel engine.

FIG. 1 a illustrates a locomotive 103 including a conventional uniflowtwo-stroke diesel engine system 101. As shown in FIGS. 1 b and 1 c, thelocomotive diesel engine system 101 of FIG. 1 a includes a conventionalair system. Referring concurrently to both FIGS. 1 b and 1 c, thelocomotive diesel engine system 101 generally comprises a turbocharger100 having a compressor 102 and a turbine 104, which provides compressedair to an engine 106 having an airbox 108, power assemblies 110, anexhaust manifold 112, and a crankcase 114. In a typical locomotivediesel engine system 101, the turbocharger 100 increases the powerdensity of the engine 106 by compressing and increasing the amount ofair transferred to the engine 106.

More specifically, the turbocharger 100 draws air from the atmosphere116, which is filtered using a conventional air filter 118. The filteredair is compressed by a compressor 102. The compressor 102 is powered bya turbine 104, as will be discussed in further detail below. A largerportion of the compressed air (or charge air) is transferred to anaftercooler 120 (or otherwise referred to as a heat exchanger, chargeair cooler, or intercooler) where the charge air is cooled to a selecttemperature. Another smaller portion of the compressed air istransferred to a crankcase ventilation oil separator 122, whichevacuates the crankcase 114 in the engine; entrains crankcase gas; andfilters entrained crankcase oil before releasing the mixture ofcrankcase gas and compressed air into the atmosphere 116.

The cooled charge air from the aftercooler 120 enters the engine 106 viaan airbox 108. The decrease in charge air intake temperature provides adenser intake charge to the engine, which reduces NO_(x) emissions whileimproving fuel economy. The airbox 108 is a single enclosure, whichdistributes the cooled air to a plurality of cylinders. The combustioncycle of a diesel engine includes, what is referred to as, scavengingand mixing processes. During the scavenging and mixing processes, apositive pressure gradient is maintained from the intake port of theairbox 108 to the exhaust manifold 112 such that the cooled charge airfrom the airbox 108 charges the cylinders and scavenges most of thecombusted gas from the previous combustion cycle.

More specifically, during the scavenging process in the power assembly110, the cooled charge air enters one end of a cylinder controlled by anassociated piston and intake ports. The cooled charge air mixes with asmall amount of combusted gas remaining from the previous cycle. At thesame time, the larger amount of combusted gas exits the other end of thecylinder via four exhaust valves and enters the exhaust manifold 112 asexhaust gas. The control of these scavenging and mixing processes isinstrumental in emissions reduction as well as in achieving desiredlevels of fuel economy.

Exhaust gases from the combustion cycle exit the engine 106 via anexhaust manifold 112. The exhaust gas flow from the engine 106 is usedto power the turbine 104 of the turbocharger 100, and thereby power thecompressor 102 of the turbocharger 100. After powering the turbine 104,the exhaust gases are released into the atmosphere 116 via an exhauststack 124 or silencer.

The exhaust gases released into the atmosphere by a locomotive dieselengine include particulates, nitrogen oxides (NO_(x)) and otherpollutants. Legislation has been passed to reduce the amount ofpollutants that may be released into the atmosphere. Traditional systemshave been implemented which reduce these pollutants, but at the expenseof fuel efficiency. Accordingly, it is an object of the presentdisclosure to provide an exhaust aftertreatment system, which reducesthe amount of pollutants (e.g., particulates, nitrogen oxides (NO_(x))and other pollutants) released by the diesel engine while achievingdesired fuel efficiency.

The various embodiments of the present aftertreatment system are able toexceed, what is referred in the industry as, the EnvironmentalProtection Agency's (EPA) Tier II (40 CFR 92), Tier III (40 CFR 1033),and Tier IV (40 CFR 1033) emission requirements, as well as the EuropeanCommission (EURO) Tier IIIb emission requirements. These variousemission requirements are cited by reference herein and made a part ofthis patent application.

SUMMARY OF THE DISCLOSURE

The present disclosure generally relates to a diesel engine and, moreparticularly, to a control system and method for an exhaustaftertreatment system for a locomotive diesel engine. In accordance withan embodiment of the present system, a two-stroke uniflow scavengeddiesel engine system including an exhaust aftertreatment system isdescribed for reducing NO_(x) emissions and achieving desired fueleconomy.

A system and method for controlling the exhaust aftertreatment system isprovided. The present system being adapted to monitor and control selectcomponents of the exhaust aftertreatment system. Specifically, thecontrol system may be adapted to control select components of an exhaustaftertreatment system to adaptively regulate filtration based on variousoperating conditions of the locomotive.

In accordance with an embodiment of the disclosure, an exhaustaftertreatment system for a locomotive is described for reducingpollutants. This system generally includes a manifold adapted to receiveexhaust from the locomotive engine and stabilize the exhaust from thelocomotive engine; a filtration system coupled to the manifold includinga catalyst and filter adapted to filter particulate matter, hydrocarbonsand carbon monoxide from the exhaust; and a NO_(x) reduction systemsituated inline with the filtration system adapted to reduce NO_(x) fromthe exhaust.

According to various aspects of the present disclosure, the exhaustaftertreatment system may include various additional features. In oneembodiment, the exhaust aftertreatment system includes a filtrationinjection system adapted to add fuel to the exhaust in the manifold,where the manifold is sized and shaped to promote mixing of the exhaustand fuel contained therein. Specifically, the fuel in this mixturereacts with oxygen in the presence of the catalyst, increasing thetemperature of the exhaust, and thereby promoting oxidation of soot onthe filter in the filtration system. The filtration system may becomprised of a diesel oxidation catalyst (DOC) or a diesel particulatefilter (DPF). A filtration control system is also described formonitoring and controlling particulate buildup on the filter.

In another embodiment, the NO_(x) reduction system may include aselective catalytic reduction (SCR) catalyst and an ammonia slipcatalyst (ASC). A NO_(x) reduction control system is also described formonitoring and controlling the NO_(x) reduction system. A NO_(x)reduction system injection system may further be provided to add aNO_(x) reduction reagent to the exhaust. The NO_(x) reduction systeminjection system is preferably situated upstream of the NO_(x) reductionsystem.

In yet another embodiment, the exhaust aftertreatment system may furtherinclude a heating device situated with respect to the manifold forheating the exhaust and a control system for the heating device.

Various embodiments of an exhaust aftertreatment system are shown anddescribed which may operate within a locomotive operating environmentand be placed within the limited size constraints of the locomotive. Inone embodiment, an exhaust aftertreatment system is shown and describedhaving a filtration system situated inline with a NO_(x) reductionsystem. In another embodiment, an exhaust aftertreatment system is shownhaving an integral housing having a filtration system and a NO_(x)reduction system. Because exhaust from a locomotive engine is generallynot uniform, the manifold may be sized and shaped to uniformlydistribute the exhaust to the filtration system. For example, themanifold may be sized and shaped such that the exhaust enters a volumegreater than the volume at which exhaust is expelled from the engine.

According to another aspect of the present disclosure, an exhaustaftertreatment system is provided for a locomotive, which includes asupport system and a connection system to the locomotive engine andstructure. The exhaust aftertreatment system includes a manifold coupledto an exhaust outlet of the locomotive engine and an emissions reductionsystem flexibly coupled to the manifold to isolate operational loads ofthe engine from the locomotive. In one example, a support structure isprovided such that the mass load of the exhaust aftertreatment system issupported by the locomotive via the support structure. In anotherexample, a connection system is provided to permit the exhaustaftertreatment system to move relative to its loads and account forthermal expansion.

These exhaust aftertreatment systems may be used in conjunction withvarious exhaust gas recirculation systems (including those describedherein) to further reduce exhaust emissions from the engine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a perspective view of a locomotive including a two-strokediesel engine system.

FIG. 1 b is a partial cross-sectional perspective view of the two-strokediesel engine system of FIG. 1 a.

FIG. 1 c is a system diagram of the two-stroke diesel engine of FIG. 1 bhaving a conventional air system.

FIG. 2 a is a system diagram of a two-stroke diesel engine having anexhaust aftertreatment system.

FIG. 2 b is a system diagram of a two-stroke diesel engine having anexhaust aftertreatment system including a selective catalytic reductioncatalyst and ammonia slip catalyst.

FIG. 2 c is a system diagram of a control system for a two-stroke dieselhaving an exhaust aftertreatment system having a NO_(x) reduction systemand a filtration system.

FIG. 3 is a system diagram of the two-stroke diesel engine system havingan EGR system in accordance with an embodiment of the presentdisclosure.

FIG. 4 is a system diagram of the two-stroke diesel engine system havingan EGR system in accordance with another embodiment of the presentdisclosure.

FIG. 5 is a system diagram of the two-stroke diesel engine system havingan EGR system in accordance with another embodiment of the presentdisclosure.

FIG. 6 is a system diagram of the two-stroke diesel engine system havingan EGR system in accordance with another embodiment of the presentdisclosure.

FIG. 7 is a system diagram of the two-stroke diesel engine system havingan EGR system in accordance with another embodiment of the presentdisclosure.

FIG. 8 is a system diagram of a control system for an EGR system for atwo-stroke diesel engine in accordance with an embodiment of the presentdisclosure.

FIG. 9 a is a perspective view of a locomotive including a two-strokediesel engine system with an EGR system in accordance with an embodimentof the present disclosure.

FIG. 9 b is a partial cross-sectional perspective view of the two-strokediesel engine system with an EGR system of FIG. 9 a.

FIG. 9 c is a top view of the two-stroke diesel engine system with anEGR system of FIG. 9 a.

FIG. 9 d is a side view of the two-stroke diesel engine system with anEGR system of FIG. 9 a, showing ducts for introducing the recirculatedexhaust gas into the engine.

FIG. 9 e is a perspective view of an embodiment of an EGR module for usewith the EGR system of FIG. 9 a.

FIG. 9 f is a side view of the EGR module of FIG. 9 e.

FIG. 9 g is a front side view of the EGR module of FIG. 9 e.

FIG. 9 h is a cross sectional view of the EGR module of FIG. 9 e.

FIG. 10 is a system diagram of a two-stroke diesel engine having anexhaust aftertreatment system and an EGR system.

FIG. 11 is a system diagram of a two-stroke diesel engine having an EGRsystem and an exhaust aftertreatment system including a selectivecatalytic reduction catalyst and ammonia slip catalyst.

FIG. 12 a is an exploded perspective view of an embodiment of an exhaustaftertreatment system in accordance with the present system.

FIG. 12 b is another perspective view of the embodiment of the exhaustaftertreatment system of FIG. 12 a.

FIG. 12 c is a bottom perspective view of the embodiment of the exhaustaftertreatment system of FIG. 12 a.

FIG. 12 d is a top view of the embodiment of the exhaust aftertreatmentsystem of FIG. 12 a.

FIG. 12 e is a top perspective view of the embodiment of the exhaustaftertreatment system of FIG. 12 a.

FIG. 12 f is a side view of the embodiment of the exhaust aftertreatmentsystem of FIG. 12 a, showing the individual exhaust aftertreatment lineassemblies thereof.

FIG. 12 g is an exploded perspective view of an embodiment of theexhaust aftertreatment system of FIG. 12 a including a connectionsystem.

FIG. 12 h is a detailed side view of the embodiment of the exhaustaftertreatment system of FIG. 12 a including a connection system.

FIG. 12 i is a perspective view of the embodiment of the exhaustaftertreatment system of FIG. 12 a including a support structure.

FIG. 12 j is a side perspective view of the embodiment of the exhaustaftertreatment system of FIG. 12 a including a support structure andconnection system.

FIG. 12 k is a detailed perspective view of the embodiment of theexhaust aftertreatment system of FIG. 12 a showing a burner.

FIG. 12 l is a partial cross-sectional perspective view of a locomotiveincluding the exhaust aftertreatment system of FIG. 12 a.

DETAILED DESCRIPTION OF THE DRAWINGS

The present system is directed to a control system for a uniflowtwo-stroke locomotive diesel engine having an exhaust aftertreatmentsystem for a locomotive diesel engine to reduce pollutants, namelyparticulate matter and NO_(x) emissions released from the engine. Thepresent exhaust aftertreatment system may be further implemented inconjunction with an exhaust gas recirculation (EGR) system whichenhances the unique scavenging and mixing processes of a locomotiveuniflow two-stroke diesel engine in order to further reduce NO_(x)emissions while achieving desired fuel economy.

The present system may further be enhanced by adapting the variousengine parameters, the EGR system parameters, and the exhaustaftertreatment system parameters. For example, as discussed above,emissions reduction and achievement of desired fuel efficiency may beaccomplished by maintaining or enhancing the scavenging and mixingprocesses in a uniflow two-stroke diesel engine (e.g., by adjusting theintake port timing, intake port design, exhaust valve design, exhaustvalve timing, EGR system design, engine component design andturbocharger design).

The various embodiments of the present disclosure may be applied tolocomotive two-stroke diesel engines having various numbers of cylinders(e.g., 8 cylinders, 12 cylinders, 16 cylinders, 18 cylinders, 20cylinders, etc.). The various embodiments may further be applied toother two-stroke uniflow scavenged diesel engine applications other thanfor locomotive applications (e.g., marine applications). The variousembodiments may also be applied to other types of diesel engines (e.g.,four-stroke diesel engines).

A control system for the exhaust aftertreatment system is provided whichmonitors and controls select components of any of the exhaustaftertreatment systems of the embodiments described below, or othersimilar exhaust aftertreatment systems. Specifically, the control systemmay be adapted to control select components of an exhaust aftertreatmentsystem to adaptively regulate filtration based on various operatingconditions of the locomotive.

As shown in FIG. 2 a, the present system may include an exhaustaftertreatment system 251 for reducing particulate matter (PM),hydrocarbons and/or carbon monoxide emissions from the exhaust manifold212 of the engine 206. In this system, the engine 206 may be adapted tohave reduced NO_(x) emissions (e.g., less than 1.3 g/bhp-hr). In orderto reduce further emissions from the exhaust, the exhaust aftertreatmentsystem 251 generally includes a filtration system 255/257 to filterother emissions including particulate matter from the exhaust. Morespecifically, the exhaust aftertreatment system 251 may include a dieseloxidation catalyst (DOC) 255 and a diesel particulate filter (DPF) 257.The DOC 255 uses an oxidation process to reduce the particulate matter(PM), hydrocarbons and/or carbon monoxide emissions in the exhaustgases. The DPF 257 includes a filter to reduce PM and/or soot from theexhaust gases. The DOC/DPF 255/257 arrangement may be adapted topassively regenerate and oxidize soot. Although a DOC 255 and DPF 257are shown, other comparable filters may be used.

A filtration control system 280 may be provided, which monitors andmaintains the cleanliness of the DPF 257. In another embodiment, acontrol system 280 determines and monitors the pressure differentialacross the DPF 257 using pressure sensors. As discussed above, theDOC/DPF arrangement 255/257 may be adapted to passively regenerate andoxidize soot within the DPF 257. However, the DPF 257 will accumulateash and some soot, which must be removed in order to maintain the DPFefficiency. As ash and soot accumulate, the pressure differential acrossthe DPF 257 increases. Accordingly, the control system 280 monitors anddetermines whether the DPF 257 has reached a select pressuredifferential at which the DPF 257 requires cleaning or replacement. Inresponse thereto, the control system 280 may signal an indication thatthe DPF 257 requires cleaning or replacement.

Alternatively, a control system 280 is shown to be coupled to a DOC/DPFdoser 261 (e.g., a hydrocarbon injector), which adds fuel onto thecatalyst for the DOC/DPF arrangement 255/257 for active regeneration ofthe filter. The fuel reacts with oxygen in the presence of the catalyst,which increases the temperature of the exhaust gas to promote oxidationof soot on the filter. In yet another embodiment, the control system 280may be coupled to a heating device 293, which may be in the form of anoptional burner or other heating element, for controlling thetemperature of the exhaust gas to control oxidation of soot on thefilter.

As shown in FIG. 2 b, the present system may include an exhaustaftertreatment system 251 for reducing NO_(x) emissions and theparticulate matter (PM), hydrocarbons and/or carbon monoxide emissionsreleased to the atmosphere 216. In this particular arrangement, theexhaust aftertreatment system 251 further includes a selective catalyticreduction (SCR) catalyst 265 and ammonia slip catalyst (ASC) 267 inaddition to a filtration system 255/257 similar to that shown anddescribed with respect to FIG. 2 a. More specifically, the exhaustaftertreatment system 251 includes a diesel oxidation catalyst (DOC)255, a diesel particulate filter (DPF) 257, a control system (forfiltration) 280 and DOC/DPF doser 261 similar to that shown anddescribed with respect to FIG. 2 a. In yet another embodiment, theexhaust aftertreatment system 251 may further include a heating elementin the form of an optional burner or other heating element forcontrolling the temperature of the exhaust gas to control oxidation ofsoot on the filter.

Additionally, the exhaust aftertreatment system 251 of FIG. 2 b furtherincludes a selective catalytic reduction (SCR) catalyst 265 and ammoniaslip catalyst (ASC) 267 adapted to lower NO_(x) emissions of the engine206. The SCR 265 and ASC 267 are further coupled to an SCR doser 263 fordosing an SCR reductant fluid or SCR reagent (e.g., urea-based, dieselexhaust fluid (DEF)), as specifically illustrated in FIG. 2 c. Uponinjection of the SCR reductant fluid or SCR reagent, the NO_(x) from theexhaust reacts with the reductant fluid over the catalyst in the SCR 265and ASC 267 to form nitrogen and water. In another embodiment, althougha urea-based SCR 265 is shown, other SCRs known in the art may also beused (e.g., hydrocarbon based SCRs, solid SCRs, De-NO_(x) systems,etc.). In yet another embodiment, the system may be adapted to lowerNO_(x) emissions prior to lowering the particulate matter (PM),hydrocarbons and/or carbon monoxide emissions. In such an arrangement,the SCR system 265/267 is located upstream of the filtration system255/257.

In one example, shown in FIG. 2 c, the present exhaust aftertreatmentsystem 251 may include a control system 280 for controlling thecleanliness of the DPF 257 similar to that shown and described withrespect to FIG. 2 a. Specifically, the control system 280 may be adaptedto control temperature of exhaust gas at the DPF 257 to promoteoxidation of the filter. As discussed above, the DOC/DPF arrangement255/257 may be adapted to passively regenerate and oxidize soot withinthe DPF 257. However, the DPF 257 will accumulate ash and some soot,which must be removed in order to maintain the DPF efficiency.Accordingly, the control system 280 monitors and determines whetherexhaust gas at the DOC/DPF arrangement 255/257 has reached a selecttemperature, at which oxidation may occur at the DPF 257. Specificallythe control system 280 monitors the temperature of exhaust gas at eitherthe DOC 255 inlet or DOC 255 outlet using temperature sensors 286 a. Itis specifically critical for the exhaust temperature to be above theselect threshold at the DPF 257 such that soot therein may be oxidized.Because exhaust temperature may decrease as exhaust flows through theDOC 255, it is preferable that the temperature sensor 286 a be situatedat the DOC 255 outlet to provide a more accurate indication of theexhaust temperature at the DPF 257.

If cleaning is desired and the exhaust temperature is not within theoxidation temperature range (e.g., between about 240° C. and about 280°C., and preferably about 280° C.), the control system 280 may signal aheating device 293 (e.g., optional burner, or other heating element) toheat a select volume of exhaust entering the exhaust aftertreatmentsystem from the exhaust manifold 212. For example, exhaust burner linesfrom the engine upstream of the turbocharger (e.g., from the engineexhaust manifold 212) may be in communication with the exhaustaftertreatment system 251, via the turbocharger mixing manifold 211, todirect a select amount of exhaust directly from the engine (e.g., fromthe engine exhaust manifold 212) to a heating device in the form of aburner or other heating element, and then to the exhaust aftertreatmentsystem 251 via the turbocharger mixing manifold 211. The select amountof exhaust is heated to a select temperature and introduced into theexhaust stream at the turbocharger mixing manifold 211. The selectamount of exhaust is preferably introduced upstream of the location ofthe DOC/DPF doser. The heated exhaust is mixed with the exhaust in theturbocharger mixing manifold 211 to achieve a temperature of betweenabout 240° C. and about 280° C., and preferably about 280° C., at whichoxidation of soot on the filter of the DOC/DPF arrangement 255/257 ispromoted. The operation of the optional heating device in the form of aburner or other heating element may be controlled by the control system280. As a result, the control system 280 promotes oxidation of soot onthe filter.

Moreover, the control system may be adapted to monitor and control thepressure differential across the DPF 257. In one embodiment, the controlsystem 280 may use a pressure differential sensor 284 b at the DPF 257for monitoring the pressure differential across the DPF 257.Specifically, a pressure sensor is situated before and after the DPF 257to determine the pressure differential thereof. As ash and sootaccumulate, the pressure differential across the DPF 257 increases. Whenthe DPF 257 is functioning properly, the pressure differential isbetween about 3.5 kPa and about 6.5 kPa. Therefore, high pressure (i.e.,above between about 3.5 kPa and about 6.5 kPa) may indicate that soothas accumulated at the DPF 257. As described above, in order to cleanthe filter, the control system 280 may be adapted to increasetemperature of exhaust gas at the DPF 257, and dose accordingly, topromote oxidation of soot on the filter.

In another embodiment, the control system may use a pressure sensor 284a at the inlet to the exhaust aftertreatment system 251 (i.e.,turbocharger adapter or mixing manifold 211) to determine backpressureof the exhaust aftertreatment system. High backpressure at theturbocharger mixing manifold 211 is indicative of soot accumulation atthe DPF 257. Thus, in response to an indication from the pressure sensor284 a, the control system 280 may be adapted to increase exhaust gastemperature at the DOC/DPF arrangement 255/257, as described above.

The control system 280 may further be adapted to create a predictivemodel for determining when the filter should be cleaned. Specifically,the control system 280 may use an emissions sensor 283 a at the exhaustaftertreatment system inlet to measure particulate matter (PM) andNO_(x) in the exhaust entering the system over a specific length oftime. Based on these measurements, the control system 280 calculates andmaps the estimated soot accumulated on the filter. As a result, it ispossible to measure the length of time it takes for the filter to becomefilled with soot, and therefore to predict when the filter will needcleaning. Thus, the control system 280 may be adapted to include openloop control to determine the operable lifespan of the filter.

Moreover, the control system 280 may be adapted to monitor PM levels ofexhaust in order to determine the health of the DPF 257. Specifically,the control system 280 may use an emissions sensor 283 b at the exhaustoutlet to measure PM levels in the exhaust. As described above, the DOC255 uses an oxidation process to reduce the particulate matter (PM),hydrocarbons and/or carbon monoxide emissions in the exhaust gases,while DPF 257 filters PM and/or soot from the exhaust gases. When PMlevels are above a select threshold (e.g., EPA Tier IV emissionsstandards referred to above), it is indicative that the DPF 257 is notfunctioning properly. Therefore, in this embodiment, if the emissionssensor 283 b indicates PM levels are higher than the select threshold,the control system 280 may signal that the DPF 257 needs to be removedand replaced.

Additionally, the control system may be coupled to a DOC/DPF doser 261(e.g., a hydrocarbon injector), which adds fuel onto the catalyst forthe DOC/DPF arrangement 255/257 for active regeneration of the filter,as described above. In order for dosing to be effective, exhausttemperature at the DOC/DPF arrangement 255/257 must be within or abovethe operational temperature range (e.g., between about 240° C. and 280°C., and preferably about 280° C.). Therefore, the control system 280 maybe adapted to control dosing such that the injector does not dose unlessthe exhaust gas temperature is within or above the oxidation range.

Moreover, the control system is adapted to monitor and control exhausttemperature at the DOC/DPF arrangement 255/257. Specifically, thecontrol system 280 uses a temperature sensor 286 b at the DOC 255, andpreferably at the DOC 255 outlet, to measure temperature of exhaust. Ifthe exhaust temperature at the DOC/DPF arrangement 255/257 is below 280°C., the control system 280, the control system 280 may be adapted toincrease exhaust temperature, as described above. However, dosing maycause the exhaust temperature at the DOC/DPF arrangement 255/257 toincrease beyond permissible operational ranges. Specifically, if theexhaust gas temperature at the DOC/DPF arrangement 255/257 is higherthan between about 550° C. and about 650° C., and preferably about 650°C., the DPF 257 unit may crack and/or the lifespan of the filter may beotherwise reduced. Therefore, the control system 280 may be adapted tocontrol dosing such that the temperature at the DOC/DPF arrangement255/257 is maintained preferably above about 280° C. and below about650° C. for effective oxidation of soot on the filter.

Additionally, the control system 280 of FIG. 2 c may be further adaptedto monitor the SCR 265 and ASC 267 arrangement, and to control NO_(x)reduction by administering the SCR reductant fluid or SCR reagentinjection based on the monitored values. Specifically, the controlsystem may use an emissions sensor at the exhaust outlet to measureNO_(x) levels in the exhaust. If the sensor indicates NO_(x) levels arehigher than a select threshold (e.g., EPA Tier IV emissions standardsreferred to above), the control system 280 may be adapted to signal tothe SCR doser to increase injection of SCR reductant fluid or SCRreagent. In contrast, the control system 280 may be adapted to signal tothe SCR doser to decrease injection of SCR reductant fluid or SCRreagent when NO_(x) levels are less than a select threshold.

Moreover, the control system may further be adapted to detect overdosingof SCR reductant fluid or SCR reagent injection by using the emissionssensor at the exhaust outlet to measure NO_(x) levels in the exhaust.Overdosing of SCR reductant fluid or SCR reagent injection generallyresults in increased NO_(x) emissions. If the sensor indicates thatNO_(x) levels are higher than a select threshold, the control system 280may be adapted to signal the SCR doser to reduce SCR reductant fluidand/or SCR reagent injection.

The control system 280 may further be adapted to control injection ofSCR reductant fluid or SCR reagent based on temperature. For example,the SCR 265 and ASC 267 may have select temperature operability ranges(e.g., between about 200° C. and about 400° C., and preferably aboveabout 230° C. and below about 400° C.), wherein the SCR 265 and ASC 267may only reduce NO_(x) at certain temperatures. In the embodimentillustrated in FIG. 2 c, the control system 280 uses a temperaturesensor 286 c at the NO_(x) reduction system 265/267, and specifically atthe dosing mixing area 273, to determine whether the exhaust gastemperature is between a select temperature range (e.g., between about230° C. and about 400° C.). In this arrangement, the control system 280may be adapted to signal the injector 263 to only operate when theexhaust temperature is within this select temperature range.

Moreover, the control system 280 may be adapted to monitor pressure atthe NO_(x) reduction system 265/267. Specifically, the exhaustaftertreatment system 251 may include a pressure sensor 284 c situatedat the NO_(x) reduction system 265/267, which is diagnostic.Specifically, if pressure is high at the NO_(x) reduction system 265/267it is generally indicative of a problem with mixing at the mixing area273. Therefore, in response to an indication from the sensor thatpressure at the NO_(x) reduction system is high, the control system 280may signal that the mixing area requires maintenance.

Additionally, the present disclosure is directed to a method forreducing emissions in exhaust expelled the engine of a locomotive havingan exhaust aftertreatment system (e.g., as shown in the embodiments ofFIGS. 2 a-2 c and their relevant disclosures). Specifically, the exhaustaftertreatment system may include a turbocharger mixing manifold adaptedto receive exhaust from the engine and a filtration system coupledthereto. The filtration system generally includes a catalyst and afilter adapted to filter particulate matter from the exhaust. Theaftertreatment system further includes a heating device coupled to theengine for heating at least a portion of the exhaust entering theturbocharger mixing manifold, wherein the turbocharger mixing manifoldis sized and shaped to promote mixing of the exhaust from the locomotiveengine and the portion of heated exhaust from the heating device. Themanifold generally delivers this mixture of engine exhaust and heatedexhaust to the filtration system. The present method includes the stepsof: (1) providing exhaust from the locomotive engine to the turbochargermixing manifold; (2) measuring exhaust temperature at the filtrationsystem; (3) adaptively delivering a select volume of exhaust from thelocomotive engine to the heating device; (4) adaptively heating theselect volume of exhaust delivered to the heating device to a selecttemperature in response to exhaust temperature values measured foradaptive temperature regulation thereof; (5) delivering the selectvolume of heated exhaust to the manifold; (6) mixing the exhaust fromthe locomotive engine and the portion of heated exhaust within in themanifold; and (7) delivering the mixed exhaust to the filtration system,wherein regulation of exhaust temperature at the filtration systempromotes oxidation of the filter, such that health of the filter ismaintained and emissions are reduced. Additionally, the present methodmay further include the step of adding fuel to the mixture of exhaustfrom the locomotive engine and the portion of heated exhaust, whereinthe fuel and exhaust mixture reacts with oxygen in the presence of thecatalyst to promote oxidation of soot on the filter.

As illustrated in FIGS. 3-9, an EGR system may be used to reduce exhaustemissions. These EGR systems may be used in conjunction with the exhaustaftertreatment systems of FIGS. 2 a and 2 b to further reduce exhaustemissions. Such emissions systems for a diesel locomotive engine whichinclude both an EGR system and an exhaust aftertreatment system aredescribed in detail with respect to FIGS. 10-11.

As shown in FIG. 3, an EGR system 350 is illustrated which recirculatesexhaust gases from the exhaust manifold 312 of the engine 306, mixes theexhaust gases with the cooled charge air of the aftercooler 320, anddelivers such to the airbox 308. In this EGR system 350, only a selectpercentage of the exhaust gases is recirculated and mixed with theintake charge air in order to selectively reduce pollutant emissions(including NO_(x)) while achieving desired fuel efficiency. Thepercentage of exhaust gases to be recirculated is also dependent on theamount of exhaust gas flow needed for powering the compressor 302 of theturbocharger 300. It is desired that enough exhaust gas powers theturbine 304 of the turbocharger 300 such that an optimal amount of freshair is transferred to the engine 306 for combustion purposes. Forlocomotive diesel engine applications, it is desired that less thanabout 35% of the total gas (including compressed fresh air from theturbocharger and recirculated exhaust gas) delivered to the airbox 308be recirculated. This arrangement provides for pollutant emissions(including NO_(x)) to be reduced, while achieving desired fuelefficiency.

A flow regulating device may be provided for regulating the amount ofexhaust gases to be recirculated. In one embodiment, the flow regulatingdevice is a valve 352 as illustrated in FIG. 3. Alternatively, the flowregulating device may be a positive flow device 360, wherein there is novalve (not shown) or the valve 352 may function as an on/off valve aswill be discussed in greater detail below.

The select percentage of exhaust gases to be recirculated may beoptionally filtered. Filtration is used to reduce the particulates thatwill be introduced into engine 306 during recirculation. Theintroduction of particulates into the engine 306 causes accelerated wearespecially in uniflow two-stroke diesel engine applications. If theexhaust gases are not filtered and recirculated into the engine, theunfiltered particulates from the combustion cycle would accelerate wearof the piston rings and cylinder liner. For example, uniflow two-strokediesel engines are especially sensitive to cylinder liner wall scuffingas hard particulates are dragged along by the piston rings the cylinderliner walls after passing through the intake ports. Oxidation andfiltration may also be used to prevent fouling and wear of other EGRsystem components (e.g., cooler 358 and positive flow device 360) orengine system components. In FIG. 3, a diesel oxidation catalyst (DOC)354 and a diesel particulate filter (DPF) 356 are provided forfiltration purposes. The DOC 354 uses an oxidation process to reduce theparticulate matter (PM), hydrocarbons and/or carbon monoxide emissionsin the exhaust gases. The DPF 356 includes a filter to reduce PM and/orsoot from the exhaust gases. The DOC/DPF arrangement 354/356 may beadapted to passively regenerate and oxidize soot. Although a DOC 354 andDPF 356 are shown, other comparable filters may be used.

The filtered air is optionally cooled using cooler 358. The cooler 358serves to decrease the recirculated exhaust gas temperature, therebyproviding a denser intake charge to the engine. The decrease inrecirculated exhaust gas intake temperature reduces NO_(x) emissions andimproves fuel economy. It is preferable to have cooled exhaust gas ascompared to hotter exhaust gas at this point in the EGR system due toease of deliverability and compatibility with downstream EGR system andengine components.

The cooled exhaust gas flows to a positive flow device 360 whichprovides for the necessary pressure increase to overcome the pressureloss within the EGR system 350 itself and overcome the adverse pressuregradient between the exhaust manifold 312 and the introduction locationof the recirculated exhaust gas. Specifically, the positive flow device360 increases the static pressure of the recirculated exhaust gassufficient to introduce the exhaust gas upstream of the power assembly.Alternatively, the positive flow device 360 decreases the staticpressure upstream of the power assembly at the introduction locationsufficient to force a positive static pressure gradient between theexhaust manifold 312 and the introduction location upstream of the powerassembly 310. The positive flow device 360 may be in the form of a rootsblower, a venturi, centrifugal compressor, propeller, turbocharger, pumpor the like. The positive flow device 360 may be internally sealed suchthat oil does not contaminate the exhaust gas to be recirculated.

As shown in FIG. 3, there is a positive pressure gradient between theairbox 308 (e.g., about 94.39 inHga) to the exhaust manifold 312 (e.g.,about 85.46 inHga) necessary to attain the necessary levels of cylinderscavenging and mixing. In order to recirculate exhaust gas, therecirculated exhaust gas pressure is increased to at least match theaftercooler discharge pressure as well as overcome additional pressuredrops through the EGR system 350. Accordingly, the exhaust gas iscompressed by the positive flow device 360 and mixed with fresh air fromthe aftercooler 320 in order to reduce NO_(x) emissions while achievingdesired fuel economy. It is preferable that the introduction of theexhaust gas is performed in a manner which promotes mixing ofrecirculated exhaust gas and fresh air.

As an alternative to the valve 352 regulating the amount of exhaust gasto be recirculated as discussed above, a positive flow device 360 mayinstead be used to regulate the amount of exhaust gas to berecirculated. For example, the positive flow device 360 may be adaptedto control the recirculation flow rate of exhaust gas air from theengine 306, through the EGR system 350, and back into the engine 306. Inanother example, the valve 352 may function as an on/off type valve,wherein the positive flow device 360 regulates the recirculation flowrate by adapting the circulation speed of the device. In thisarrangement, by varying the speed of the positive flow device 360, avarying amount of exhaust gas may be recirculated. In yet anotherexample, the positive flow device 360 is a positive displacement pump(e.g., a roots blower) which regulates the recirculation flow rate byadjusting its speed.

A new turbocharger 300 is provided having a higher pressure ratio thanthat of the prior art uniflow two-stroke diesel engine turbochargers.The new turbocharger provides for a higher compressed charge of freshair, which is mixed with the recirculated exhaust gas from the positiveflow device 360. The high pressure mixture of fresh air and exhaust gasdelivered to the engine 306 provides the desired trapped mass of oxygennecessary for combustion given the low oxygen concentration of thetrapped mixture of fresh air and cooled exhaust gas.

As shown in an EGR system 450 embodiment of FIG. 4, recirculated exhaustgas may be alternatively introduced upstream of the aftercooler 420 andcooled thereby before being directed to the airbox 408 of the engine406. In this embodiment, the aftercooler 420 (in addition to the cooler458) cools the fresh charge air from the turbocharger 400 and therecirculated exhaust gas to decrease the overall charge air intaketemperature of the engine 406, thereby providing a denser intake chargeair to the engine 406. In another embodiment (not shown), an optionaloil filter may be situated downstream of the positive flow device 460 tofilter any residual oil therefrom. This arrangement prevents oilcontamination in the aftercooler 420 and in the recirculated exhaustgas.

As shown in an EGR system 550 embodiment of FIG. 5, the filtered air mayoptionally be directed to the aftercooler 520 for the same purposeswithout the addition of the cooler 358, 458 in FIGS. 3 and 4. In thisarrangement, the cooling of the exhaust gas to be recirculated isperformed solely by the aftercooler 520. The aftercooler 520 would serveto cool the fresh charge air from the turbocharger and the recirculatedexhaust gas, thereby providing a denser overall intake charge air to theengine.

As shown in FIG. 6, an EGR system 650 is illustrated which does notinclude the DOC/DPF filtration system of the previous embodiments.

As shown in FIG. 7, an EGR system 750 is illustrated, which isimplemented in an engine 706 having a positive or negative crankcaseventilation, whereby the oil separator outlet is directed to the lowpressure region upstream of the compressor inlet. Accordingly, thecompressed air from the turbocharger 700 is not directed to an oilseparator as shown in the previous embodiments.

A control system may further be provided which monitors and controlsselect components of any of the EGR systems of the previous embodiments,or other similar EGR systems. Specifically, the control system may beadapted to control select components of an EGR system to adaptivelyregulate exhaust gas recirculation based on various operating conditionsof the locomotive. The control system may be in the form of a locomotivecontrol computer, another onboard control computer or other similarcontrol device. Various embodiments of control systems are illustratedin FIG. 8.

In one embodiment of FIG. 8, a control system 880 monitors thetemperature of the exhaust gas at the exhaust manifold using exhaustmanifold temperature sensors 882 a, 882 b. If the exhaust gastemperature at the exhaust manifold 812 is within the normal operationaltemperature range of the EGR system, the control system signals the flowregulating device (e.g., valve 852 a and 852 b and/or positive flowdevice 860) to recirculate a select amount of exhaust gas through theengine. If the exhaust gas temperature falls outside of the normaloperational temperature range of the EGR system, the control system 880signals the flow regulating device (e.g., valve 852 a, 852 b and/orpositive flow device 860) to recirculate another select amount ofexhaust gas through the engine. It is preferable that if the exhaust gastemperature falls outside of the normal operational temperature range ofthe EGR system, the control system 880 signals the flow regulatingdevice to lower the amount of exhaust to be recirculated through theengine. In one example, the normal operational temperature range of theEGR system is based in part on the operating temperature limits of thediesel engine. In another example, the normal operational temperaturerange of the EGR system is based in part on the temperatures at whichthe DPF 856 a, 856 b will passively regenerate. The control system mayfurther be adapted to signal the flow regulating device to recirculate aselect amount of exhaust gas through the engine system based in part onthe operational condition of the diesel engine system within a tunnel.In one example, the normal operational temperature range of the EGRsystem is based in part on the operation of the locomotive in a tunnel.

In another embodiment, a control system 880 monitors the oxygenconcentration in the airbox or, alternatively, the exhaust gas oxygenconcentration at the exhaust manifold 812 using oxygen concentrationsensors 884 a, 884 b. The control system 880 signals the flow regulatingdevice (e.g., valve 852 a, 852 b and/or positive flow device 860) torecirculate a select amount of exhaust gas through the engine based onlevels of oxygen concentration. In one example, if there is a highoxygen concentration, the control system 880 may be adapted to signalthe flow regulating device to increase the amount of exhaust gas to berecirculated through the engine.

In yet another embodiment, a control system 880 monitors ambienttemperature using an ambient temperature sensor 886. The control system880 signals the flow regulating device (e.g., valve 852 a, 852 b and/orpositive flow device 860) to recirculate a select amount of exhaust gasthrough the engine based on ambient temperature. In one example, if theambient temperature is lower than a select temperature, the controlsystem 880 may be adapted to signal the flow regulating device toincrease the amount of exhaust gas to be recirculated through the engineto at least offset the higher levels of oxygen concentration in therecirculated exhaust gas at lower ambient temperatures.

In yet another embodiment, a control system 880 monitors ambientbarometric pressure or altitude using an ambient barometric pressuresensor 888 or an altitude measurement device 890. The control system 880signals the flow regulating device (e.g., valve 852 a, 852 b and/orpositive flow device 860) to recirculate a select amount of exhaust gasthrough the engine based on ambient barometric pressure or altitude. Inone example, if the barometric pressure is lower than a select value,the control system 880 may be adapted to signal the flow regulatingdevice to decrease the amount of exhaust gas to be recirculated throughthe engine because there are lower levels of oxygen concentration in therecirculated exhaust gas at lower barometric pressures. Alternatively,if the altitude is lower than a select value, the control system 880 maybe adapted to signal the flow regulating device to increase the amountof exhaust gas to be recirculated through the engine because there arehigher levels of oxygen concentration in the recirculated exhaust gas atlower altitudes.

In another embodiment, a control system 880 determines and monitors thepressure differential across the DOC/DPF arrangement 854 a, 856 a, 854b, 856 b using pressure sensors 892 a, 892 b, 894 a, 894 b. As discussedabove, the DOC/DPF arrangement 854 a, 856 a, 854 b, 856 b may be adaptedto passively regenerate and oxidize soot within the DPF 856 a, 856 b.However, the DPF 856 a, 856 b will accumulate ash and some soot, whichmust be removed in order to maintain the DPF efficiency. As ash and sootaccumulates, the pressure differential across the DOC/DPF arrangement854 a, 856 a, 854 b, 856 b increases. Accordingly, the control system880 monitors and determines whether the DOC/DPF arrangement 854 a, 856a, 854 b, 856 b has reached a select pressure differential at which theDPF 856 a, 856 b requires cleaning or replacement. In response thereto,the control system 880 may signal an indication that the DPF 856 a, 856b requires cleaning or replacement. Alternatively, the control system880 may signal the flow regulating device to lower recirculation ofexhaust gas through the engine. In another embodiment, a control system880 is shown to be coupled to a DOC/DPF doser 896 a, 896 b, which addsfuel onto the catalyst for the DOC/DPF arrangement 854 a, 856 a, 854 b,856 b for active regeneration of the filter. The fuel reacts with oxygenin the presence of the catalyst which increases the temperature of therecirculated exhaust gas to promote oxidation of soot on the filter. Inanother embodiment (not shown), the control system may be coupled to aheating device in the form of a burner or other heating element forcontrolling the temperature of the recirculated exhaust gas to controloxidation of soot on the filter.

In yet another embodiment, a control system 880 measures the temperatureof the exhaust gas downstream of the cooler 858 or the temperature ofthe coolant in the cooler 858. As shown in FIG. 8, temperature sensors898 a, 898 b are provided for measuring exhaust gas temperaturedownstream of the cooler 858. If the exhaust gas temperature downstreamof the cooler 858 or the coolant temperature is within a selecttemperature range, the control system 880 signals the flow regulatingdevice (e.g., valve 852 a, 852 b and/or positive flow device 860) torecirculate a select amount of exhaust gas through the engine. If theexhaust gas temperature downstream of the cooler 858 or the coolanttemperature falls outside of a select temperature range, the controlsystem 880 signals the flow regulating device to recirculate anotherselect amount of exhaust gas through the engine. In one example, thecontrol system 880 may be adapted to monitor the coolant temperature todetermine whether the conditions for condensation of the recirculatedexhaust gas are present. If condensation forms, acid condensate may beintroduced into the engine system. Accordingly, the control system 880may be adapted to signal the flow regulating device to lowerrecirculation of exhaust gas through the engine until the conditions forcondensation are no longer present.

In another embodiment, a control system 880 may be adapted to adaptivelyregulate flow based on the various discrete throttle positions of thelocomotive in order to maximize fuel economy, reduce NO_(x) emissionseven further and maintain durability of the EGR system and enginecomponents. For example, the control system 880 may signal the flowregulating device (e.g., valve 852 a, 852 b and/or positive flow device860) to lower recirculation of exhaust gas through the engine at lowidle, high idle, throttle position 1, throttle position 2 or uponapplication of dynamic brake. The control system 880 may be adapted tosignal the flow regulating device to recirculate exhaust gas through theengine at or above throttle position 3. In one example, the controlsystem 880 may be adapted to increase the amount of exhaust gas to berecirculated through the engine with an increase of throttle position.In yet another embodiment, the control system 880 may be adapted toincrease the amount of exhaust gas to be recirculated with additionalengine load. Likewise, the control system 880 may be adapted to decreasethe amount of exhaust gas to be recirculated with a decreased engineload.

FIGS. 9 a-h illustrate an embodiment of an EGR system 950 in accordancewith the system outlined in FIG. 4 for use with a two-stroke,12-cylinder diesel engine system 101 in a locomotive 103. The EGR system950 is sized and shaped to fit within limited length, width, and heightconstraints of a locomotive 103. As shown herein, the EGR system 950 isinstalled within the same general framework of traditional modern dieselengine locomotives. Specifically, the EGR system 950 is generallylocated in the limited space available between the exhaust manifold 912of a locomotive engine and the locomotive radiators 980. In thisembodiment, the EGR system 950 is shown located generally above thegeneral location of the equipment rack 982. Also, a 12-cylinderlocomotive diesel engine may be used instead of a 16-cylinder locomotivediesel engine in order to provide for more space. In an alternativeembodiment (not shown), the EGR system 950 may be housed in thelocomotive body near the inertial filter.

Generally, the EGR system 950 includes a DOC, DPF and cooler, which arepackaged in an integrated EGR module 945. The EGR system 950 furtherincludes a positive flow device 960 interconnected with the EGR module945. The EGR system 950 receives exhaust gases from the exhaust manifold912 of the engine 906. A valve 952 is provided between the exhaustmanifold 912 and the integrated EGR module 945. The EGR module 945processes the exhaust gases therein. The positive flow device 960compresses the processed exhaust gas to be recirculated and introducessuch upstream of the aftercooler 920 by mixing the recirculated exhaustgases with the fresh charge air from the turbocharger 900, and deliversthe mixture of fresh charge air and recirculated exhaust gas to theairbox 908, as fully discussed with respect to the embodiment of FIG. 4.In this system, only a select percentage of the exhaust gases isrecirculated and mixed with the intake charge air in order toselectively reduce pollutant emissions (including NO_(x)) whileachieving desired fuel efficiency. Although the EGR system 950 is animplementation of the system embodiment of FIG. 4, it may be adapted tobe an implementation of any of the other previous EGR system embodimentsdiscussed herein. For example, instead of introducing the recirculatedexhaust gas upstream of the aftercooler, as described with respect tothe embodiments of FIGS. 4 and 9, the recirculated exhaust gas may beintroduced downstream of the aftercooler as discussed with respect toFIG. 3.

The integrated EGR module 945 includes a section 962 having an inlet 964for receiving exhaust gases from the exhaust manifold 912. Specifically,the inlet section 962 of the EGR module 945 is interconnected with theexhaust manifold 912 of the engine 906. A valve 952 is provided betweenthe exhaust manifold 912 and the inlet section 962 of the EGR module945. In one example, the valve 952 is adaptable for determining theamount of exhaust gases to be recirculated through the engine 906. Inanother example, the valve 953 may act as an on/off valve fordetermining whether gases are to be recirculated through the engine 906.

Having received exhaust gas, the inlet section 962 of the EGR module 945directs exhaust gases into a section which houses at least one dieseloxidation catalyst/diesel particulate filter (DOC/DPF) arrangement 953.Each DOC 954 uses an oxidation process to reduce the particulate matter,hydrocarbons and carbon monoxide emissions in the exhaust gases. EachDPF 956 includes a filter to reduce diesel particulate matter (PM) orsoot from the exhaust gases. Oxidation and filtration is specificallyused in this embodiment to reduce the particulate matter that will beintroduced into engine 906 during recirculation. The introduction ofparticulates into the engine 906 causes accelerated wear especially inuniflow two-stroke diesel engine applications. Oxidation and filtrationmay also be used to prevent fouling and wear of other EGR systemcomponents (e.g., cooler 958 and positive flow device 960) or enginesystem components.

The DOC/DPF arrangement 953 is designed, sized and shaped such that theyeffectively reduce particulate matter under the operating parameters ofthe EGR system 950, fit within the limited size constraints of thelocomotive 103, have a reasonable pressure drop across their substrates,and have a manageable service interval.

It is desirable that the DOC/DPF arrangement 953 reduces the PM in theexhaust gas by over 90% under the operating parameters of the EGR system950. Specifically, the composition of the substrates and coatingsthereon are chosen of the DOC/DPF arrangement 953 to efficiently reduceparticulate matter. In one example of a 12-cylinder uniflow scavengedtwo-stroke diesel engine at about 3,200 bhp with less than 20% exhaustgas being recirculated at full load, the DOC/DPF arrangement 953 isselected to manage and operate a mass flow of exhaust gas of from about1.5 to about 2.5 lbm/s, having an intake temperature ranging from about600° F. to about 1,050° F., and an intake pressure of about 80 inHga toabout 110 inHga. It is further preferable that the DOC/DPF arrangement953 can handle a volumetric flow rate across both the DOC/DPF from about1,000 CFM to about 1,300 CFM. Furthermore, the DOC/DPF arrangement 953is further designed to endure an ambient temperature range of about −40°C. to about 125° C.

The DOC/DPF arrangement 953 is generally packaged such that it fitswithin the size constraints of the locomotive 103. As shown in thisembodiment, each DOC 954 and DPF 956 is packaged in a cylindricalhousing similar to those commonly used in the trucking industry. EachDOC 954 and DPF 956 has a diameter of about 12 inches. The length ofeach DOC 954 is about 6 inches, whereas the length of each DPF 956 isabout 13 inches. The DOC 954 and DPF 946 are integrated within the EGRmodule 945 such that they are able to fit within the size constraints ofthe locomotive.

It is further desirable that the DOC/DPF arrangement 953 is selected tohave a reasonable pressure drop across their substrates. As discussedabove, it is preferable that the exhaust gas is introduced into a regionof higher pressure. Accordingly, it is desirable to minimize thepressure drop across the DOC/DPF arrangement 953. In one embodiment, itis desirable for the pressure drop across both substrates to be lessthan about 20 inH₂O.

Finally, it is desirable that the DOC/DPF arrangement 953 has amanageable service life. The DOC/DPF arrangement 953 accumulates ash andsome soot, which is preferably discarded in order to maintain theefficiency of the DOC 954 and the DPF 956. In one example, the serviceinterval for cleaning of the DOC/DPF arrangement 953 may be selected atabout 6 months. As shown in the embodiments, each DOC 954 and DPF 956 ishoused in separate but adjoining sections of the EGR module 945 suchthat they are removable for cleaning and replacement. For maintenance,the DOC/DPF arrangement 953 includes a flange 966 for mounting theDOC/DPF arrangement 953 together with the inlet section 962 of the EGRmodule 945 to the cooler 958. The fasteners associated with the mountingflange 966 of the DOC/DPF arrangement 953 may be removed such that theDOC/DPF arrangement 953 together with the inlet section 962 of the EGRmodule 945 may be removed from the cooler 958 and the locomotive.Thereafter, the inlet section 962, the DOC 954, and the DPF 956 may beselectively disassembled for service via flanges 968, 970. In order tofacilitate serviceability, the fasteners for flanges 968, 970 are offsetfrom the DOC/DPF arrangement 953 mounting flange 966. Accordingly, theDOC/DPF arrangement 953 together with the inlet section 962 may beremoved via its mounting flange 966 without first disassembling eachindividual section.

In order to meet the operational and maintainability requirements of theEGR system 950, a plurality of DOCs and DPFs are paired in parallelpaths. For example, as shown, two DOC/DPC arrangement pairs are shown inparallel in this embodiment in order to accommodate the flow andpressure drop requirements of the EGR system 950. Moreover, the DOC/DPFarrangement pairs in parallel provide for reasonable room foraccumulation of ash and soot therein. Nevertheless, more or less DOC/DPFarrangement pairs may be placed in a similar parallel arrangement inorder to meet the operational and maintainability requirements of theEGR system 950.

The integrated EGR module 945 further includes a cooler 958interconnected to the DOC/DPF arrangement 953. The cooler 958 decreasesthe filtered exhaust gas temperature, thereby providing a denser intakecharge to the engine 906. In one example of a cooler 958 for a12-cylinder uniflow scavenged two-stroke diesel engine at about 3200 bhpwith less than 20% exhaust gas being recirculated at full load, each DPF956 extends into the cooler 958 and provides filtered exhaust gas at amass flow of about 1.5 lbm/s to about 2.5 lbm/s; a pressure of about 82inHga to about 110 inHga; and a density of about 0.075 lbm/ft³ to about0.15 lbm/ft³. It is desirable that the cooler 958 reduces thetemperature of the filtered exhaust gas from a range of about 600°F.-1,250° F. to a range of about 200° F.-250° F. at an inlet volumetricflow rate of about 1,050 CFM to about 1,300 CFM. The source of thecoolant for the cooler 958 may be the water jacket loop of the engine,having a coolant flow rate of about 160 gpm to about 190 gpm via coolantinlet 972. It is further desirable that the cooler 958 maintains areasonable pressure drop therein. As discussed above, the exhaust gas isintroduced into a region of higher pressure. Accordingly, it isdesirable to minimize the pressure drop within the cooler 958. In oneembodiment, it is desirable for the pressure drop across the cooler tobe from about 3 inH₂O to about 6 inH₂O.

The cooler 958 is generally packaged such that it fits within the sizeconstraints of the locomotive 103. As shown in this embodiment, thecooler 958 is integrated with the DOC/DPF arrangement 953. The cooler958 has a frontal area of about 25 inches by 16 inches, and a depth ofabout 16 inches.

The EGR module 945 is connected to a positive flow device 960 via theoutlet 974 from the cooler 958. The positive flow device 960 regulatesthe amount of cooled, filtered exhaust gas to be recirculated andintroduced into the engine 906 at the aftercooler 920 upstream of itscore via ducts 976. Specifically, the positive flow device 960 isillustrated as a variable speed roots style blower, which regulates therecirculation flow rate by adapting the circulation speed of the devicethrough its inverter drive system. Specifically, by varying the speed ofthe positive flow device 960, a varying amount of exhaust gas may berecirculated. Other suitable positive flow devices may be implemented inorder to similarly regulate the amount of exhaust gases to berecirculated.

As shown in FIG. 10, an exhaust aftertreatment system 1051 similar tothat shown and described with respect to FIG. 2 a may be used inconjunction with an EGR system to reduce exhaust emissions. The EGRsystem 1050 may be similar to those shown and described with respect toany of FIGS. 3-9. Specifically, the exhaust aftertreatment system 1051may be adapted to reduce particulate matter (PM), hydrocarbons and/orcarbon monoxide emissions. In this particular arrangement, the exhaustaftertreatment system 1051 further includes a generally includes afiltration system 1055/1057 similar to that shown and described withrespect to FIG. 2 a. More specifically, the exhaust aftertreatmentsystem 1051 includes a diesel oxidation catalyst (DOC) 1055, a dieselparticulate filter (DPF) 1057, a control system (for filtrationmonitoring and/or control) 1080 and DOC/DPF doser 1061 similar to thatshown and described with respect to FIG. 2 a.

As shown in FIG. 11, an exhaust aftertreatment system 1151 similar tothat shown and described with respect to FIGS. 2 b and 2 c may be usedin conjunction with an EGR system to reduce exhaust emissions. The EGRsystem 1150 may be similar to those shown and described with respect toany of FIGS. 3-9. Specifically, the exhaust aftertreatment system 1151may be adapted to reduce NO_(x) in addition to particulate matter (PM),hydrocarbons and/or carbon monoxide emissions. In this particulararrangement, the exhaust aftertreatment system 1151 generally includes afiltration system and SCR system similar to that shown and describedwith respect to FIGS. 2 b and 2 c. More specifically, the exhaustaftertreatment system 1151 includes a diesel oxidation catalyst (DOC)1155, a diesel particulate filter (DPF) 1157, a control system (forfiltration and SCR monitoring and/or control) 1180 and DOC/DPF doser1161 similar to that shown and described with respect to FIG. 2 a.Additionally, the exhaust aftertreatment system 1151 of FIG. 11 furtherincludes a selective catalytic reduction (SCR) catalyst 1165, ammoniaslip catalyst (ASC) 1167, and an SCR doser 1163 adapted to lower NO_(x)emissions of the engine 1106.

FIGS. 12 a-12 l illustrate an embodiment of an exhaust aftertreatmentsystem 1251 in accordance with the system outlined in FIGS. 2 b, 2 c and11 for use with a locomotive 103. The exhaust aftertreatment system 1251is adapted to reduce NO_(x) in addition to particulate matter (PM),hydrocarbons and/or carbon monoxide emissions. In this particulararrangement, the exhaust aftertreatment system 1251 generally includes aplurality of filtration systems 1255/1257, each being situated inlinewith a NO_(x) reduction system 1265/1267.

The exhaust aftertreatment system 1251 includes a turbocharger mixingmanifold 1211 for receiving exhaust expelled from the engine 1206 and,specifically, the turbocharger 1200.

Multiple discrete aftertreatment line assemblies 1268-1271 are providedin order to accommodate and treat the exhaust gas from the engine 1206.Specifically, the exhaust gas from the engine 1206 is separated based onspecific operating parameters of each of the inline filtration systems1255/1257 and NO_(x) reduction systems 1265/1267, described below. Asshown herein, the turbocharger mixing manifold 1211 separates and guidesthe exhaust gas into a plurality of discrete exhaust aftertreatment lineassemblies 1268-1271 to promote uniform distribution of exhaust gas intothe subsequent inline filtration system 1255/1257 and NO_(x) reductionsystem 1265/1267 of the exhaust aftertreatment system 1251. Thearrangement of discrete aftertreatment line assemblies 1268-1271 furtherpromotes thermal isolation and distribution of mass loading of theexhaust aftertreatment system 1251.

The exhaust gas in each of the exhaust aftertreatment line assemblies1271 is then further distributed into a plurality of discrete exhaustgas lines 1272-1274 via line assembly distribution manifolds 1285-1288.Each of the discrete exhaust gas lines 1272-1274 comprises an inlinefiltration system 1255/1257 and a NO_(x) reduction system 1265/1267.

Each inline filtration system 1255/1257 includes a DOC/DPF arrangementto reduce particulate matter (PM), hydrocarbons and/or carbon monoxideemissions exhaust gas. As shown herein, and specifically illustrated inFIG. 12 h, the housing section associated with the DPF 1257 facilitatesthe removal of the DPF 1257 filters for cleaning and maintainability

DOC/DPF dosers (e.g., hydrocarbon injectors) may be provided to add aselect amount of fuel into the exhaust stream at the turbocharger mixingmanifold 1211. The DOC/DPF dosers may be arranged with respect to theturbocharger mixing manifold 1211 to facilitate delivery of fuel to theexhaust contained within the turbocharger mixing manifold 1211 andpromote mixing therein. The DOC/DPF dosers may be situated in a commonrail or single line system. The operation of the DOC/DPF doser may becontrolled by a control system as described with respect to theembodiment described in FIGS. 2 b and 2 c. The fuel reacts with oxygenin the presence of the catalyst, which increases the temperature of theexhaust gas to promote oxidation of soot on the filter of the DOC/DPFarrangement 1255/1257. The turbocharger mixing manifold 1211 may furtherbe sized and shaped to serve as a mixing chamber, promote mixing of fueland exhaust, and uniformly distribute this mixture to the remainder ofthe exhaust aftertreatment system 1251. In yet another embodiment (notshown), mixing elements may be included to promote mixing in theturbocharger mixing manifold 1211 or elsewhere upstream of the DOC/DPFarrangement 1255/1257.

Thereafter, the filtered exhaust gas is then mixed with an SCR reductantfluid or SCR reagent (e.g., urea-based, diesel exhaust fluid, ammonia orhydrocarbon) in a line leading to a NO_(x) reduction system 1289. Forexample, the SCR reductant fluid or SCR reagent may be introduced by anSCR doser upstream of the SCR 1265 (e.g., mixing region at 1273). TheSCR reductant fluid or SCR reagent is preferably introduced to each ofthe of the exhaust aftertreatment line assemblies 1268-1271 using acommon rail or single line system. The operation of the SCR doser may becontrolled by a control system as described with respect to theembodiment described in FIG. 2 b. Upon injection of the SCR reductantfluid or SCR reagent, the NO_(x) from the filtered exhaust reacts withthe SCR reductant fluid or SCR reagent over the catalyst in the SCR 1265and ASC 1267 to form nitrogen and water. Although a urea-based SCR 1265is shown, other SCR's known in the art may also be used (e.g.,hydrocarbon based SCR's, De-NO_(x) systems, etc.). The exhaust is thenreleased into the atmosphere via a plurality of exhaust stacks1224-1227.

In yet another embodiment, an optional heating device, such as a burner,or other heating element, may be used to control the temperature of theexhaust at the exhaust aftertreatment system 1251 turbocharger mixingmanifold 1211 to control oxidation of soot on the filter of the DOC/DPFarrangement 1255/1257. For example, as shown in FIGS. 12 b-12 e, exhaustburner lines 1259 from the engine upstream of the turbocharger 1200(e.g., from the engine exhaust manifold 1212) are shown in communicationwith the exhaust aftertreatment system 1251 via the turbocharger mixingmanifold 1211 to direct a select amount of exhaust directly from theengine (e.g., from the engine exhaust manifold 1212) to a heating devicein the form of a burner (shown at 1293) or other heating element, andthen to the turbocharger mixing manifold 1211 of the exhaustaftertreatment system 1251 (see also FIG. 12 k). The select amount ofexhaust is heated to a select temperature and introduced into theexhaust stream at the turbocharger mixing manifold 1211. The selectamount of exhaust is preferably introduced upstream of the location ofthe DOC/DPF doser. The heated exhaust is mixed with the exhaust in theturbocharger mixing manifold 1211 to achieve a temperature of betweenabout 240° C. and about 280° C., and preferably about 280° C., at whichoxidation of soot on the filter of the DOC/DPF arrangement 1255/1257 ispromoted. The operation of the optional heating device may be controlledby a control system as described with respect to the embodimentdescribed in FIGS. 2 b and 2 c.

The pressure and mass flow of exhaust exiting the turbocharger stack isgenerally non-uniform and varies based on throttle position of thelocomotive. However, it is preferable that the pressure and mass flow ofexhaust to each inline filtration system 1255/1257 and NO_(x) reductionsystem 1265/1267 be uniform. Accordingly, the turbocharger mixingmanifold 1211 may further be sized and shaped to stabilize the exhaustairflow and promote uniform exhaust airflow to each inline filtration1255/1257 and NO_(x) reduction system 1265/1267. Accordingly, as shownin FIG. 12 g, the turbocharger mixing manifold 1211 is sized and shapedsuch that the exhaust generally enters a volume (or static box), whichis greater than the turbocharger exit. Specifically, exhaust gas fromthe turbocharger 1210 enters the mixing chamber that has a volumegreater than the volume of the mixing manifold intake (see, FIG. 12 e).This larger volume stabilizes (or slows) the exhaust airflow and allowsit to homogenize such that it may then uniformly enter into to theindividual exhaust aftertreatment line assemblies 1268-1271, eachincluding an inline filtration system 1255/1257 and NO_(x) reductionsystem 1265/1267.

The exhaust aftertreatment system 1251 is sized and shaped to fit withinlimited length, width, and height constraints of a locomotive 103. Asshown herein, the exhaust aftertreatment system 1251 is installed withinthe same general framework of traditional modern diesel enginelocomotives. In the embodiment shown (see FIGS. 12 a, 12 b and 12 l),the exhaust aftertreatment system 1251 is generally located in thelimited space available above the locomotive engine 1206 within thelocomotive car body frame 1275.

The exhaust aftertreatment system 1251 is constructed to withstand theoperational loading environment of the locomotive 103. Specifically, itis required that the exhaust aftertreatment system 1251 be connected tothe engine 1206 (and specifically the turbocharger stack) to receiveexhaust therefrom. However, the engine 1206 cannot support the mass loadof the exhaust aftertreatment system 1251. It is therefore preferablethat the mass load of the exhaust aftertreatment system 1251 besupported by the locomotive body frame 1275 via a support structure 1277including a plurality of support beams 1279, rather than the engine1206. At the same time, as illustrated in FIGS. 12 i and 12 j, it ispreferable that the operational loads associated with the engine 1206are isolated from the operational loads associated with the locomotivestructure. A hood 1291 may also be provided having a ventilation systemfor releasing heat created by the exhaust aftertreatment system 1251.

The various embodiments of the present disclosure may be applied to bothlow and high pressure loop EGR systems. The various embodiments of thepresent disclosure may be applied to locomotive two-stroke dieselengines may be applied to engines having various numbers of cylinders(e.g., 8 cylinders, 12 cylinders, 16 cylinders, 18 cylinders, 20cylinders, etc.). The various embodiments may further be applied toother two-stroke uniflow scavenged diesel engine applications other thanfor locomotive applications (e.g., marine applications).

As discussed above, NO_(x) reduction is accomplished through the exhaustaftertreatment system while the new engine components maintain thedesired levels of cylinder scavenging and mixing in a uniflow scavengedtwo-stroke diesel engine. The scavenging and mixing processes may befurther enhanced by adjusting the intake port timing, intake portdesign, exhaust valve design, exhaust valve timing, exhaustaftertreatment system design, EGR system design, engine component designand turbocharger design.

The various embodiments of the present disclosure may be applied to bothlow and high pressure loop EGR systems. The various embodiments of thepresent disclosure may be applied to locomotive two-stroke dieselengines may be applied to engines having various numbers of cylinders(e.g., 8 cylinders, 12 cylinders, 16 cylinders, 18 cylinders, 20cylinders, etc.). The various embodiments may further be applied toother two-stroke uniflow scavenged diesel engine applications other thanfor locomotive applications (e.g., marine applications).

While this system and method has been described with reference tocertain illustrative aspects, it will be understood that thisdescription shall not be construed in a limiting sense. For example, thevarious operating parameters or values described herein exemplifyrepresentative values for the present system operating under certainconditions. Accordingly, it is expected that these values will changeaccording to different locomotive operating parameters or conditions.Rather, various changes and modifications can be made to theillustrative embodiments without departing from the true spirit, centralcharacteristics and scope of the disclosure, including thosecombinations of features that are individually disclosed or claimedherein.

Furthermore, it will be appreciated that any such changes andmodifications will be recognized by those skilled in the art as anequivalent to one or more elements of the following claims, and shall becovered by such claims to the fullest extent permitted by law. Forexample, the various operating parameters or values described hereinexemplify representative values for the present system operating undercertain conditions. Accordingly, it is expected that these values willchange according to different locomotive operating parameters orconditions. In another example, although a urea-based SCR is shown,other SCR's known in the art may also be used (e.g., hydrocarbon basedSCR's, De-NO_(x) systems, etc.).

1. An exhaust aftertreatment system for reducing emissions in exhaustexpelled from an engine of a locomotive, the exhaust aftertreatmentsystem comprising: a manifold adapted to receive exhaust from thelocomotive engine, a heating device coupled to the engine for heating atleast a portion of the exhaust entering the manifold, a valve forregulating the amount of exhaust delivered to the heating device,wherein said manifold is sized and shaped to promote mixing of theexhaust from the locomotive engine and the portion of heated exhaustfrom the heating device, a filtration system coupled to the manifoldincluding a catalyst and a filter adapted to filter particulate matterfrom the exhaust, wherein a select amount of fuel is added to themixture of exhaust from the locomotive engine and the portion of heatedexhaust from the heating device, and wherein the fuel and exhaustmixture reacts with oxygen in the presence of the catalyst to promoteoxidation of soot on the filter, and a control system for monitoringexhaust temperature at the filtration system, said control system beingcoupled to the valve for adaptively controlling a select volume ofexhaust to be delivered to the heating device and being coupled to theheating device for adaptively heating such select volume of exhaust to aselect temperature in response to monitored exhaust temperature valuesat the filtration system for adaptive temperature regulation thereof,wherein regulation of exhaust temperature at the filtration systempromotes oxidation of the filter, such that health of the filter ismaintained and emissions are reduced.
 2. The exhaust aftertreatmentsystem of claim 1, wherein the filtration system has an operationaltemperature range.
 3. The exhaust aftertreatment system of claim 2,wherein the operational temperature range of the filtration system isbetween about 240° C. and about 650° C., and wherein the control systemis adapted to signal the valve to deliver a select volume of exhaust tothe heating device and adapted to signal the heating device to heat suchselect volume of exhaust to a select temperature to achieve an exhausttemperature at the filtration system within its operational temperaturerange.
 4. The exhaust aftertreatment system of claim 2, wherein theselect amount of fuel is zero when the temperature at the filtrationsystem is outside its operational temperature range.
 5. The exhaustaftertreatment system of claim 1, wherein the filtration system includesa diesel particulate filter.
 6. The exhaust aftertreatment system ofclaim 1, wherein the temperature of the filtration system is measured atthe diesel particulate filter.
 7. The exhaust aftertreatment system ofclaim 5, wherein the filtration system further includes a dieseloxidation catalyst situated upstream of the diesel particulate filter,and the temperature of the filtration system is monitored at the outletof the diesel oxidation catalyst.
 8. The exhaust aftertreatment systemof claim 5, wherein the filtration system includes a diesel oxidationcatalyst situated upstream of the diesel particulate filter, and thetemperature of the filtration system is measured at the inlet of thediesel oxidation catalyst.
 9. The exhaust aftertreatment system of claim1, wherein the control system further includes a pressure differentialsensor for monitoring and controlling pressure differential across thefilter, and wherein the control system is adapted to signal the valve todeliver a select volume of exhaust to the heating device and adapted tosignal the heating device to heat such select volume of exhaust to aselect temperature to achieve a temperature at the filtration system forreducing such pressure differential across the filter.
 10. The exhaustaftertreatment system of claim 1, wherein the control system furtherincludes at least one pressure sensor situated at the manifold formeasuring backpressure of the exhaust aftertreatment system, and whereinthe control system is adapted to signal the valve to deliver a selectvolume of exhaust to the heating device and adapted to signal theheating device to heat such select volume of exhaust to a selecttemperature to achieve a temperature for reducing such backpressure. 11.The exhaust aftertreatment system of claim 1, wherein the control systemfurther includes at least one emissions sensor situated at an outlet thefiltration system for monitoring emissions therefrom, and wherein thecontrol system is adapted to signal the valve to deliver a select volumeof exhaust to the heating device and adapted to signal the heatingdevice to heat such select volume of exhaust to a select temperature toachieve a temperature for reducing emissions at such outlet.
 12. Theexhaust aftertreatment system of claim 1, further including a NO_(x)reduction system having a select operational temperature range, andwherein the control system is adapted to signal the valve to deliver aselect volume of exhaust to the heating device and adapted to signal theheating device to heat such select volume of exhaust to a selecttemperature to achieve a temperature within the operational temperaturerange of the NO_(x) reduction system.
 13. A control system for anexhaust aftertreatment system for reducing emissions in exhaust expelledfrom an engine of a locomotive, wherein the exhaust aftertreatmentsystem includes a manifold adapted to receive exhaust from thelocomotive engine, a heating device coupled to the engine for heating atleast a portion of the exhaust entering the manifold, wherein themanifold is sized and shaped to promote mixing of the exhaust from thelocomotive engine and the portion of heated exhaust from the heatingdevice, a filtration system coupled to the manifold including a catalystand a filter adapted to filter particulate matter from the exhaust, thecontrol system comprising: a sensor for measuring exhaust temperature atthe filtration system, a valve for adaptively controlling a selectvolume of exhaust to be delivered to the heating device, and a heatingdevice for adaptively heating the select volume of exhaust delivered tothe heating device, said heating device adaptively heating the selectvolume to a select temperature in response to exhaust temperature valuesmeasured by said sensor at the filtration system for adaptivetemperature regulation thereof.
 14. The control system of claim 13,wherein the filtration system has an operational temperature range ofbetween about 240° C. and about 650° C., and wherein the valve isadapted to deliver a select volume of exhaust to said heating device andwherein said heating device is adapted to heat such select volume ofexhaust to a select temperature to achieve a temperature at thefiltration system within its operational temperature range.
 15. Thecontrol system of claim 13, wherein the filtration system includes adiesel particulate filter, and wherein the temperature of the filtrationsystem is measured at the diesel particulate filter.
 16. The controlsystem of claim 13, wherein the filtration system further includes adiesel oxidation catalyst and a diesel particulate filter situateddownstream thereof, and wherein the temperature of the filtration systemis measured at the outlet of the diesel oxidation catalyst.
 17. Thecontrol system of claim 15, wherein the filtration system includes adiesel oxidation catalyst and a diesel particulate filter situateddownstream thereof, and wherein the temperature of the filtration systemis measured at the inlet of the diesel oxidation catalyst.
 18. Thecontrol system of claim 13, further including a pressure differentialsensor for monitoring and controlling pressure differential across thefilter, and wherein the valve is adapted to deliver a select volume ofexhaust to said heating device and wherein said heating device isadapted to heat such select volume of exhaust to a select temperature toachieve a temperature at the filtration system for reducing suchpressure differential across the filter.
 19. The control system of claim13, wherein the heating device is a burner.
 20. The control system ofclaim 13, further including at least one pressure sensor situated at themanifold for measuring backpressure of the exhaust aftertreatmentsystem, and wherein the valve is adapted to deliver a select volume ofexhaust to said heating device and wherein said heating device isadapted to heat such select volume of exhaust to a select temperature toachieve a temperature at the filtration system for reducing suchbackpressure.
 21. The control system of claim 13, further including atleast one emissions sensor situated at an outlet the filtration systemfor monitoring emissions therefrom, and wherein the valve is adapted todeliver a select volume of exhaust to said heating device and whereinsaid heating device is adapted to heat such select volume of exhaust toa select temperature to achieve a temperature at the filtration systemfor reducing emissions at such outlet.
 22. The control system of claim13, wherein the exhaust aftertreatment system further includes a NO_(x)reduction system having a select operational temperature range, andwherein the valve is adapted to deliver a select volume of exhaust tosaid heating device and wherein said heating device is adapted to heatsuch select volume of exhaust to a select temperature to achieve atemperature within the operational temperature range of the NO_(x)reduction system.
 23. The control system of claim 13, further includinga fuel injection device adapted to add a select amount of fuel to themixture of exhaust from the locomotive engine and the portion of heatedexhaust from the heating device, and wherein the fuel and exhaustmixture reacts with oxygen in the presence of the catalyst to promoteoxidation of soot on the filter.
 24. A method for reducing emissions inexhaust expelled from an engine of a locomotive having an exhaustaftertreatment system, wherein the exhaust aftertreatment systemincludes a manifold adapted to receive exhaust from the locomotiveengine, a heating device coupled to the engine for heating at least aportion of the exhaust entering the manifold, wherein the manifold issized and shaped to promote mixing of the exhaust from the locomotiveengine and the portion of heated exhaust from the heating device, afiltration system coupled to the manifold including a catalyst and afilter adapted to filter particulate matter from the exhaust, the methodcomprising the steps of: providing exhaust from the locomotive engine tothe manifold of the exhaust aftertreatment system, measuring exhausttemperature at the filtration system, adaptively delivering a selectvolume of exhaust from the locomotive engine to the heating device,adaptively heating the select volume of exhaust delivered to the heatingdevice to a select temperature in response to exhaust temperature valuesmeasured for adaptive temperature regulation thereof, delivering theselect volume of heated exhaust to the manifold, mixing the exhaust fromthe locomotive engine and the portion of heated exhaust within in themanifold, and delivering the mixed exhaust to the filtration system,wherein regulation of exhaust temperature at the filtration systempromotes oxidation of the filter, such that health of the filter ismaintained and emissions are reduced.
 25. The method for reducingemissions of claim 24, further including the step of adding fuel to themixture of exhaust from the locomotive engine and the portion of heatedexhaust, wherein the fuel and exhaust mixture reacts with oxygen in thepresence of the catalyst to promote oxidation of soot on the filter.